Viscoelastic polyurethane foam with aqueous polymer dispersion

ABSTRACT

A reaction system for forming a viscoelastic polyurethane foam includes an isocyanate component that has at least one isocyanate and an isocyanate-reactive component that is a mixture formed by adding at least a polyol component, an additive component, and a preformed aqueous polymer dispersion. The mixture includes, based on the total weight of the mixture, from 50.0 wt % to 99.8 wt % of a polyol component including at least one polyether polyol, from 0.1 wt % to 50.0 wt % of an additive component including at least one catalyst, and from 0.1 wt % to 6.0 wt % of a preformed aqueous polymer dispersion. The preformed aqueous polymer dispersion has a solids content from 10 wt % to 80 wt %, based on the total weight of the preformed aqueous polymer dispersion, and is one of an aqueous acid polymer dispersion or an aqueous acid modified polyolefin polymer dispersion in which the polyolefin is derived from at least one C 2  to C 20  alpha-olefin.

FIELD

Embodiments relate to viscoelastic polyurethane foams prepared using apreformed aqueous polymer dispersion and a method of manufacturing suchviscoelastic polyurethane foams.

Introduction

Flexible, viscoelastic polyurethane foam (also known as slow-recoveryfoam and high-damping foam) is characterized by relatively slow, gradualrecovery from compression and the viscoelastic foam may have arelatively lower resiliency. Exemplary applications for viscoelasticfoam utilize the foam's characteristics such as shape conforming, energyattenuating, and/or sound damping. For example, the viscoelasticpolyurethane foam may be used in comfort applications (such as beddingand pillows), shock absorbing applications (such as in athletic paddingand helmets), and in soundproof applications (such as automotiveinteriors).

SUMMARY

Embodiments may be realized by providing a reaction system for forming aviscoelastic polyurethane foam that has a resiliency of less than orequal to 20% as measured according to ASTM D 3574, the reaction systemincluding an isocyanate component that has at least one isocyanate andan isocyanate index of the reaction system is from 50 to 110; and anisocyanate-reactive component that is a mixture formed by adding atleast a polyol component, an additive component, and a preformed aqueouspolymer dispersion. The mixture includes from 50.0 wt % to 99.8 wt % ofa polyol component, based on the total weight of the mixture, the polyolcomponent including at least one polyether polyol, from 0.1 wt % to 50.0wt % of an additive component, based on the total weight of the mixture,that includes at least one catalyst, and from 0.1 wt % to 6.0 wt % of apreformed aqueous polymer dispersion, based on the total weight of themixture. The preformed aqueous polymer dispersion has a solids contentfrom 10 wt % to 80 wt %, based on the total weight of the preformedaqueous polymer dispersion, and is one of an aqueous acid polymerdispersion or an aqueous acid modified polyolefin polymer dispersion inwhich the polyolefin is derived from at least one C₂ to C₂₀alpha-olefin.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an exemplary schematic representation of amelt-extrusion apparatus used to prepare a preformed aqueous polymerdispersion.

FIG. 2 illustrates the wetting effect of Working Example 12.

FIG. 3 illustrates the wetting effect of Comparative Example D.

DETAILED DESCRIPTION

A viscoelastic polyurethane foam may be characterized as having aresiliency that is less than or equal to 20% as measured according toASTM D 3574 (may also be referred to as a Ball Rebound Test). Forexample, the resiliency may be less than 15%, less than 10%, less than8%, and/or less than 7 wt %. The resiliency may be greater than 1%.Viscoelastic polyurethane foams may be prepared using a reaction systemthat includes an isocyanate component and an isocyanate-reactivecomponent. In particular, the viscoelastic foam is formed as thereaction product of the isocyanate component and the isocyanate-reactivecomponent. The isocyanate component includes at least one isocyanatesuch as an isocyanate-terminated prepolymer and/or a polyisocyanate. Theisocyanate-reactive component includes at least one compound having anisocyanate reactive hydrogen atom group, such as a hydroxyl group and/oran amine group. The isocyanate component and/or the isocyanate-reactivecomponent may include an additive such a catalyst, a curing agent, asurfactant, a blowing agent, a polyamine, and/or a filler.

According to embodiments, the isocyanate-reactive component includes atleast three components. In particular, the isocyanate-reactive componentincludes a polyol component, an additive component, and a preformedaqueous polymer dispersion.

The polyol component accounts for 50.0 wt % to 99.8 wt % (e.g., 60.0 wt% to 99.8 wt %, 70.0 wt % to 99.5 wt %, 80.0 wt % to 99.0 wt %, 90.0 wt% to 99.0 wt %, etc., so as to be the majority component in the reactionsystem for forming the viscoelastic polyurethane foam) of theisocyanate-reactive component. The polyol component includes at leastone polyether polyol and may optionally include at least one polyesterpolyol.

The additive component may include a catalyst, a curing agent, asurfactant, a blowing agent, a polyamine, water, and/or a filler. Theadditive component accounts for 0.1 wt % to 50.0 wt % (e.g., 0.1 wt % to40.0 wt %, 0.1 wt % to 30.0 wt %, 0.1 wt % to 20.0 wt %, 0.1 wt % to15.0 wt %, 0.1 wt % to 10.0 wt %, 0.1 wt % to 5.0 wt %, etc.) of theadditive component, based on the total weight of the isocyanate-reactivecomponent. The additive component in exemplary embodiments includes atleast one catalyst and at least one surfactant.

The preformed aqueous polymer dispersion accounts for 0.1 wt % to 6.0 wt% (e.g., 0.1 wt % to 5.0 wt %, 0.1 wt % to 4.1 wt %, 0.1 wt % to 4.0 wt%, 0.1 wt % to 3.5 wt %, 0.1 wt % to 3.0 wt %, 0.4 wt % to 2.5 wt %, 0.5wt % to 2.4 wt %, etc.) of the isocyanate-reactive component. Thepreformed aqueous polymer dispersion is one of an aqueous acid polymerdispersion or an aqueous acid-modified polyolefin polymer dispersion inwhich the polyolefin is derived from at least one C₂ to C₂₀ alpha-olefin(e.g., at least one C₂ to C₁₀ alpha-olefin and/or C₂ to C₈alpha-olefin). The preformed aqueous polymer dispersion has a solidscontent from 10 wt % to 80 wt %, based on the total weight of thepreformed aqueous polymer dispersion. The aqueous polymer dispersion maybe a combination of one or more aqueous polymer dispersions that areused to form the viscoelastic polyurethane foam.

The viscoelastic foam prepared using the preformed aqueous polymerdispersion additive may have an air flow greater than 5.0 standard cubicfoot per minute (scfm) (approximately 2.4 L/s) under standardconditions. The viscoelastic foam may have a recovery time (alsoreferred to as viscoelastic recovery time) of less than 20 seconds(e.g., less than 10 seconds and/or less than 5 seconds). For example, aviscoelastic polyurethane foam may be prepared that has an increased airflow without sacrificing resiliency.

Preformed Aqueous Polymer Dispersion

The aqueous polymer dispersion includes at least (a) a base polymerincluding an acid polymer and/or an acid-modified polyolefin polymer and(b) a fluid medium (in this case water), in which the base polymer isdispersed in the fluid medium. The preformed aqueous polymer dispersionmay be a continuous liquid phase component at ambient conditions of roomtemperature and atmospheric pressure and is derived from a liquid phase(i.e., the fluid medium) and a solid phase (i.e., the base polymer).

In embodiments, the preformed aqueous polymer dispersion is one of anaqueous acid polymer dispersion or an aqueous acid-modified polyolefinpolymer dispersion in which the polyolefin is derived from at least oneC₂ to C₂₀ alpha-olefin. By aqueous acid polymer dispersion it is meantan aqueous dispersion prepared with an acid based polymer. By aqueousacid-modified polyolefin polymer dispersion it is meant an aqueousdispersion prepared with an acid-modified polyolefin polymer. By derivedfrom at least one C₂ to C₂₀ alpha-olefin it is meant that the polyolefinis a polymer prepared using at least one alpha-olefin, in which eachalpha-olefin used is one of a C₂ to C₂₀ alpha-olefin (e.g., thepolyolefin may be derived from at least one of ethylene, propylene,butylene, hexene, and/or octene). In exemplary embodiments, thepolyolefin may be an ethylene based polymer and/or a propylene basedpolymer

As used herein, by polymer it meant a compound prepared by polymerizingmonomers, whether of the same or a different type. Thus, the termpolymer embraces the term homopolymer, usually employed to refer topolymers prepared from only one type of monomer, and the terminterpolymer. It also embraces all forms of interpolymers, e.g., random,block, homogeneous, heterogeneous, etc. By copolymer/interpolymer it ismeant a polymer prepared by the polymerization of at least two differenttypes of monomers. These terms include both classical copolymers, i.e.,polymers prepared from two different types of monomers, and polymersprepared from more than two different types of monomers, e.g.,terpolymers, tetrapolymers, etc.

By ethylene based polymer it is meant a polymer that includes a majorityweight percent polymerized ethylene monomer (based on the total weightof polymerizable monomers), and optionally may comprise at least onepolymerized comonomer different from ethylene (such as at least oneselected from a C₃ to C₂₀ alpha-olefin) so as to form an ethylene-basedinterpolymer. For example, when the ethylene-based polymer is anethylene-propylene copolymer, the amount of ethylene may be greater than50 wt %, based on the total weight to the copolymer. “Units derived fromethylene” and like terms mean the units of a polymer that formed fromthe polymerization ethylene monomers.

By propylene based polymer it is meant a polymer that includes amajority weight percent polymerized propylene monomer (based on thetotal weight of polymerizable monomers), and optionally may comprise atleast one polymerized comonomer different from propylene (such as atleast one selected from a C₂ and C₄ to C₂₀ alpha-olefin) so as to forman propylene-based interpolymer. For example, when the propylene-basedpolymer is a propylene-ethylene copolymer, the amount of propylene maybe greater than 50 wt %, based on the total weight to the copolymer.“Units derived from propylene” and like terms mean the units of apolymer that formed from the polymerization propylene monomers.

Exemplary aqueous acid polymer dispersion may include ethylene-acrylicacid interpolymers, ethylene-methacrylic acid interpolymers, and/orethylene-crotonic acid interpolymers. The ethylene-acrylic acidinterpolymer is prepared by the copolymerization of at least ethyleneand acrylic acid. The ethylene-methacrylic acid interpolymer is preparedby copolymerization of at least ethylene and methacrylic acid. Theethylene-crotonic acid interpolymer is prepared by copolymerization ofat least ethylene and crotonic acid. It is understood that in such anaqueous acid polymer dispersion, exemplary embodiments are not limitedto just ethylene-acrylic acid interpolymers, ethylene-methacrylic acidinterpolymers, and/or ethylene-crotonic acid interpolymers. For example,ethylene can be copolymerized with more than one of the following:acrylic acid, methacrylic acid, and/or crotonic acid.

Exemplary aqueous acid polymer dispersions may include at least oneethylene-acrylic acid (EAA) copolymer (and/or ethylene-methacrylic acidcopolymer) as the base polymer that is dispersed in the fluid medium (inthis case water). The dispersion may be enabled by BLUEWAVE™ Technology,which is a proprietary and patented mechanical-dispersion technologythat is a trademark of The Dow Chemical Company or an affiliated companyof The Dow Chemical Company. For example, the EAA may be prepared bycopolymerization of ethylene with acrylic acid, which yieldsethylene-acrylic acid EAA copolymers. The ethylene-acrylic acidcopolymer may have an acrylic acid content of at least 10 wt % (e.g.,from 10 wt % to 70 wt %, from 10 wt % to 60 wt %, from 10 wt % to 50 wt%, from 10 wt % to 40 wt %, from 10 wt % to 30 wt %, and/or from 15 wt %to 25 wt %). Exemplary EAA copolymers are available as PRIMACOR™products, available from THE DOW CHEMICAL COMPANY. The EAA copolymer mayhave a melt index from 100 to 2000 g/10 minute (ASTM Method D-1238 at190° C. and 2.16 kg). The EAA copolymer may have a Brookfield viscosityfrom 5,000 to 13,000 cps at 350° F., and is available from The DowChemical Company.

The ethylene-methacrylic acid copolymer may be prepared bycopolymerization of ethylene with methacrylic acid. Exemplary,ethylene-acrylic acid, ethylene-methacrylic acid, and/orethylene-crotonic acid copolymers are discussed in U.S. Pat. No.4,599,392 and/or U.S. Pat. No. 4,988,781.

Exemplary aqueous acid-modified polyolefin polymer dispersions includedispersions sold as HYPOD™ products, available from The Dow ChemicalCompany. The HYPOD™ products may be enabled by BLUEWAVE™ Technology,which is a proprietary and patented mechanical-dispersion technologythat is a trademark of The Dow Chemical Company or an affiliated companyof The Dow Chemical Company. BLUEWAVE™ Technology may utilize ahigh-shear mechanical process that may work by taking traditionalthermoplastic polymers and elastomers and breaking them up intosubmicron particles. The aqueous acid-modified polymer dispersions mayinclude propylene based dispersions and ethylene-based dispersions,which may combine the performance of high-molecular-weightthermoplastics and elastomers with the application advantages of ahigh-solids waterborne dispersion. The polyolefin of the dispersion maybe a metallocene catalyzed polyolefin. Exemplary polyolefins are sold inthe AFFINITY™, ENGAGE™, VERSIFY™, and INFUSE™ products, available fromThe Dow Chemical Company.

The aqueous polymer dispersion may be prepared by using a neutralizingagent. Exemplary neutralizing agents include ammonia, ammoniumhydroxide, potassium hydroxide, sodium hydroxide, lithium hydroxide, andcombinations thereof. For example, if a polar group of the base polymeris acidic or basic in nature, the polymer may be partially or fullyneutralized with a neutralizing agent to form a corresponding salt. Withthe acid polymer modified dispersion prepared using EAA is used, theneutralizing agent is a base, such as ammonium hydroxide, potassiumhydroxide, and/or sodium hydroxide. Those having ordinary skill in theart will appreciate that the selection of an appropriate neutralizingagent may depend on the specific composition formulated, and that such achoice is within the knowledge of those of ordinary skill in the art.

The aqueous polymer dispersion may be prepared in an extrusion process,e.g., as discussed in U.S. Pat. No. 8,318,257. FIG. 1 illustrates anexemplary a schematic diagram of an extrusion apparatus formanufacturing an aqueous polymer dispersions. An extruder 1 (such as atwin screw extruder) may be coupled to a pressure control device 2 (suchas a pressure control valve, a back pressure regulator, a melt pump,and/or a gear pump). A neutralizing agent reservoir 3 and an initialwater reservoir 4, each of which includes a pump (not shown), may beprovided in connection with the extruder 1. The desired amounts ofneutralizing agent and initial water are provided from the neutralizingagent reservoir 3 and the initial water reservoir 4, respectively. Anysuitable pump may be used, e.g., based on the desired flow. Theneutralizing agent and initial water may be preheated in a preheater.

Polymer resin (such as an acid polymer and/or a polyolefin polymer) maybe fed from the feeder 7 to an inlet 8 of the extruder 1, where theresin is melted or compounded. The polymer resin may be provided in theform of pellets, powder, and/or flakes, for example. A dispersing agentmay be added to the extruder through and along with the polymer resin ormay be provided separately to the extruder 1. For example, the polymer(and dispersing agent if included) may be melted, mixed, and conveyed byscrews in a mix and convey zone. The polymer resin melt is thendelivered from the mix and convey zone to an emulsification zone of theextruder where the initial amounts of water and neutralizing agent (fromthe reservoirs 3 and 4) are added through an inlet 5. The resultantemulsified mixture may be further diluted at least one time using anadditional water via inlet 9 from reservoir 6 in a dilution and coolingzone of the extruder 1. As would be understood by a person of ordinaryskill in the art, at least in view of U.S. Pat. No. 8,318,257, thedilution scheme of the resultant emulsified mixture may be varied (e.g.,based on the desired solids content). For example, the emulsifiedmixture may be further diluted with additional dispersion medium fromadditional reservoirs in a dilution zone of the extruder 1. Thedispersion may be diluted to at least 30 weight percent dispersion inthe dilution zone.

With respect to the screws in the mix and convey zone, one or morerotating restriction orifices may be located along the screw. Therotating restriction orifice may improve stability of the dispersionforming process. Non-rotating restriction orifices may be used. Thescrews may include high-mixing kneading disks, in some embodiments. Inaddition to the high-mixing kneading disks described above andoptionally low free volume kneading disks, which may minimize the volumeweighted particle size distribution of dispersions formed using theextruder 1.

The extruder 1 includes high internal phase emulsion creation (HIPE)zones along a length thereof, e.g., as discussed in U.S. Pat. No.8,318,257. For example, the aqueous polymer dispersion may be preparedusing a system that incorporates 12 HIPE zones, in which the temperatureis varied in the zones. Depending upon the feed composition (such as thepolymer, dispersing agent, neutralizing agent, etc.), it may bedesirable to have a longer or a shorter HIPE zones. Multiple dispersionmedium injection points may be provided to allow the HIPE zones to beextended or shortened as needed. As the particle size of the dispersedpolymer particles is formed in the HIPE zone, adequate mixing should beprovided to develop the desired particle size. Having a variable lengthfor the HIPE zone may allow for a broader range of polymers to beprocessed in a single extruder, providing for process flexibility, amongother benefits.

The twin screw extruder barrels, screws, and dilution medium injectionpoints may be varied such that the length to diameter (L/D) of the HIPEzone is at least 16 when producing EEA containing dispersions. Theapparatuses described above may be used to produce dispersions, where,in some embodiments, the polymer feed rate may range from about 50 toabout 2000 lb/h (about 22 to about 907 kg/h). In other embodiments, thepolymer feed rate may range from about 100 to about 1000 lb/h (betweenabout 45 and about 454 kg/h). In other embodiments, the screw speed mayrange from about 300 rpm to about 1200 rpm. In yet other embodiments,the extruder discharge pressure may be maintained at a pressure rangingfrom about 300 to about 800 psig (from about 21 bar to about 56 bar).

Polyol Component

The polyol component includes at least one polyether polyol and/orpolyester polyol. Exemplary polyether polyols are the reaction productof alkylene oxides (such as at least one ethylene oxide, propyleneoxide, and/or butylene oxide) with initiators containing from 2 to 8active hydrogen atoms per molecule. Exemplary initiators includeethylene glycol, diethylene glycol, propylene glycol, dipropyleneglycol, butane diol, glycerol, trimethylolpropane, triethanolamine,pentaerythritol, sorbitol, ethylene diamine, toluene diamine,diaminodiphenylmethane, polymethylene polyphenylene polyamines,ethanolamine, diethanolamine, and mixtures of such initiators. Exemplarypolyols include VORANOL™ products, available from The Dow ChemicalCompany. The polyol component may include polyols that are useable toform viscoelastic polyurethane foams.

For example, the polyol component may include apolyoxyethylene-polyoxypropylene polyether polyol that has an ethyleneoxide content of at least 50 wt %, that has a nominal hydroxylfunctionality from 2 to 6 (e.g., 2 to 4), and has a number averagemolecular weight from 500 g/mol to 5000 g/mol (e.g., 500 g/mol to 4000g/mol, from 600 g/mol to 3000 g/mol, 600 g/mol to 2000 g/mol, 700 g/molto 1500 g/mol, and/or 800 g/mol to 1200 g/mol). Thepolyoxyethylene-polyoxypropylene polyether polyol that has an ethyleneoxide content of at least 50 wt % may account for 5 wt % to 90 wt %(e.g., 10 wt % to 90 wt %, 35 wt % to 90 wt %, 40 wt % to 85 wt %, 50 wt% to 85 wt %, 50 wt % to 80 wt %, and/or 55 wt % to 70 wt %) of theisocyanate-reactive component. The polyoxyethylene-polyoxypropylenepolyether polyol that has an ethylene oxide content of at least 50 wt %may be the majority component in the isocyanate-reactive component.

The polyol component may include a polyoxypropylene-polyoxyethylenepolyether polyol that has an ethylene oxide content of less than 20 wt %that has a nominal hydroxyl functionality from 2 to 6 (e.g., 2 to 4) andhas a number average molecular weight greater than 1000 g/mol (orgreater than 1500 g/mol) and less than 6000 g/mol. For example, themolecular weight may be from 1500 g/mol to 5000 g/mol, 1600 g/mol to5000 g/mol, 2000 g/mol to 4000 g/mol, and/or 2500 g/mol to 3500 g/mol.The polyoxypropylene-polyoxyethylene polyether polyol that has anethylene oxide content of less than 20 wt % may account for 5 wt % to 90wt % (e.g., 5 wt % to 70 wt %, 5 wt % to 50 wt %, 10 wt % to 40 wt %,and/or 10 wt % to 30 wt %) of the isocyanate reactive component. Thepolyoxypropylene-polyoxyethylene polyether polyol that has an ethyleneoxide content of less than 20 wt % may be in a blend with thepolyoxypropylene polyether polyol that has an ethylene oxide content ofat least 50 wt %, whereas the latter of which is included in a greateramount.

The polyol component may include a polyoxypropylene polyether polyolthat has a nominal hydroxyl functionality from 2 to 6 (e.g., 2 to 4) andhas a number average molecular weight from 500 g/mol to 5000 g/mol(e.g., 500 g/mol to 4000 g/mol, from 600 g/mol to 3000 g/mol, 600 g/molto 2000 g/mol, 700 g/mol to 1500 g/mol, and/or 800 g/mol to 1200 g/mol).The polyoxypropylene polyether polyol may account for 5 wt % to 90 wt %(e.g., 5 wt % to 70 wt %, 5 wt % to 50 wt %, 10 wt % to 40 wt %, and/or10 wt % to 30 wt %) of the isocyanate reactive component. Thepolyoxypropylene polyether polyol may be in a blend with thepolyoxypropylene polyether polyol that has an ethylene oxide content ofat least 50 wt %, whereas the latter of which is included in a greateramount.

In an exemplary embodiment, the polyol component may include a blend ofthe polyoxyethylene-polyoxypropylene polyether polyol that has anethylene oxide content of at least 50 wt %, thepolyoxyethylene-polyoxypropylene polyether polyol that has an ethyleneoxide content of less than 20 wt %, and the polyoxypropylene polyetherpolyol.

The polyol component may be mixed with the preformed aqueous polymerdispersion (and optionally at least part of the additive component)before contacting the isocyanate component.

Additive Component

The additive component is separate from the components that form thepreformed aqueous dispersion and the polyol component. The additivecomponent is part of the isocyanate-reactive component, but otheradditives may be incorporated into the isocyanate component. Theadditive component may include a catalyst, a curing agent, acrosslinker, a surfactant, a blowing agent (aqueous and non-aqueous,separate from the aqueous polymer dispersion), a polyamine, aplasticizer, a fragrance, a pigment, an antioxidant, a UV stabilizer,water (separate from the aqueous polymer dispersion), and/or a filler.Other exemplary additives include a chain extender, flame retardant,smoke suppressant, drying agent, talc, powder, mold release agent,rubber polymer (“gel”) particles, and other additives that are known inthe art for use in viscoelastic foams and viscoelastic foam products.

The additive component may include tin catalyst, zinc catalyst, bismuthcatalyst, and/or amine catalyst. The total amount of catalyst in theisocyanate-reactive component may be from 0.1 wt % to 3.0 wt %.

A surfactant may be included in the additive component, e.g., to helpstabilize the foam as it expands and cures. Examples of surfactantsinclude nonionic surfactants and wetting agents such as those preparedby the sequential addition of propylene oxide and then ethylene oxide topropylene glycol, solid or liquid organosilicones, and polyethyleneglycol ethers of long chain alcohols. Ionic surfactants such as tertiaryamine or alkanolamine salts of long chain alkyl acid sulfate esters,alkyl sulfonic esters, and alkyl arylsulfonic acids may be used. Forexample, the formulation may include a surfactant such as anorganosilicone surfactant. The total amount of an organosiliconesurfactant in the isocyanate-reactive component may be from 0.1 wt % to5.0 wt %, 0.1 wt % to 3.0 wt %, 0.1 wt % to 2.0 wt %, and/or 0.1 wt % to1.0 wt %.

The additive component may include water, which is separate from thepreformed aqueous polymer dispersion. The water may account for lessthan 2.0 wt % of the total weight of isocyanate-reactive component. Thetotal water, including water from the preformed aqueous polymerdispersion and water from the additive component, may account for lessthan 5 wt % of the total weight of isocyanate-reactive component.

The additive component may exclude any conventional polyurethane foamchemical cell openers based on the use of the aqueous polymerdispersion. The additive component may exclude polybutene,polybutadiene, and waxy aliphatic hydrocarbons such as oils (e.g.,mineral oil, paraffin oil, and/or naphthenic oil) that are commonlyemployed cell openers in low resiliency foams. The additive componentmay exclude cell openers that are polyols derived primarily fromalkoxylation of α,β-alkylene oxides having at least 4 carbon atoms,e.g., as discussed U.S. Pat. No. 4,596,665. The additive component mayexclude cell openers that are polyethers of up to about 3500 molecularweight that contain a high proportion (usually 50 percent or higher) ofunits derived from ethylene oxide or butylene oxide, e.g., as discussedin the background section of U.S. Pat. No. 4,863,976. The additivecomponent may exclude cell openers that are polyether polyols having amolecular weight of at least 5000 and having at least 50 wt % ofoxyethylene units, e.g., as discussed in the claims of U.S. Pat. No.4,863,976.

Isocyanate Component

The isocyanate component includes at least one isocyanate. Theisocyanate component is present at an isocyanate index from 50 to 110(e.g., from 60 to 100, from 65 to 100, from 70 to 100, from 74 to 100,from 70 to 90, from 70 to 85, and/or from 74 to 85). The isocyanateindex is defined as the molar stoichiometric excess of isocyanatemoieties in a reaction mixture with respect to the number of moles ofisocyanate-reactive units (active hydrogens available for reaction withthe isocyanate moiety), multiplied by 100. An isocyanate index of 100means that there is no stoichiometric excess, such that there is 1.0mole of isocyanate groups per 1.0 mole of isocyanate-reactive groups,multiplied by 100.

The isocyanate component may include one or more isocyanate such aspolyisocyanate and/or isocyanate-terminated prepolymer. The isocyanatemay be isocyanate-containing reactants that are aliphatic,cycloaliphatic, alicyclic, arylaliphatic, and/or aromaticpolyisocyanates or derivatives thereof. Exemplary derivatives includeallophanate, biuret, and NCO (isocyanate moiety) terminated prepolymer.For example, the isocyanate component may include at least one aromaticisocyanate, e.g., at least one aromatic polyisocyanate or at least oneisocyanate-terminated prepolymer derived from an aromaticpolyisocyanate. The isocyanate component may include at least one isomerof toluene diisocyanate (TDI), crude TDI, at least one isomer ofdiphenyl methylene diisocyanate (MDI), crude MDI, and/or higherfunctional methylene polyphenyl polyisocyanate. Examples include TDI inthe form of its 2,4 and 2,6-isomers and mixtures thereof and MDI in theform of its 2,4′-, 2,2′- and 4,4′-isomers and mixtures thereof. Themixtures of MDI and oligomers thereof may be crude or polymeric MDIand/or a known variant of MDI comprising urethane, allophanate, urea,biuret, carbodiimide, uretonimine and/or isocyanurate groups. Exemplaryisocyanates include VORANATE™ M 220 (a polymeric methylene diphenyldiisocyanate available from The Dow Chemical Company). Other exemplarypolyisocyanate include tolylene diisocyanate (TDI), isophoronediisocyanate (IPDI) and xylene diisocyanates (XDI), and modificationsthereof.

Viscoelastic Foam

The viscoelastic polyurethane foam may be useful in a variety ofpackaging applications, comfort applications (such asmattresses—including mattress toppers, pillows, furniture, seatcushions, etc.) shock absorber applications (such as bumper pads, sportand medical equipment, helmet liners, etc.), and noise and/or vibrationdampening applications (such as earplugs, automobile panels, etc.).

The viscoelastic polyurethane foam may be prepared in a slabstockprocess (e.g., as free rise foam), a molding process (such as in a boxfoaming process), or any other process known in the art. In a slabstockprocess, the components may be mixed and poured into a trough or otherregion where the formulation reacts, expands freely in at least onedirection, and cures. Slabstock processes are generally operatedcontinuously at commercial scales. In a molding process, the componentsmay be mixed and poured into a mold/box (heated or non-heated) where theformulation reacts, expands without the mold in at least one direction,and cures.

The viscoelastic polyurethane foam may be prepared at initial ambientconditions (i.e., room temperature ranging from 20° C. to 25° C. andstandard atmospheric pressure of approximately 1 atm). For example, theviscoelastic polyurethane foam may include an acid polymer and/or anacid-modified polyolefin polymer (e.g., a polymer that has a meltingpoint above 100° C.) without requiring heating or application ofpressure to the isocyanate-reactive component. Foaming at pressure belowatmospheric condition can also be done, to reduce foam density andsoften the foam. Foaming at pressure above atmospheric condition can bedone, to increase foam density and therefore the foam load bearing asmeasured by indentation force deflection (IFD). In a molding processing,the viscoelastic polyurethane foam may be prepared at initial moldtemperature above ambient condition, e.g., 50° C. and above. Overpackingof mold, i.e. filling the mold with extra foaming material, can be doneto increase foam density.

The calculated total water content for the reaction system used to formthe viscoelastic foam may be less than 5 wt %, less than 3 wt %, lessthan 2.0 wt %, and/or less than 1.6 wt %, based on the total weight ofthe reaction system for forming the viscoelastic polyurethane foam. Thecalculated total water content is calculated as the total amount of DI(deionized water) added to the formulation plus the amount of wateradded to the formulation as part of the preformed aqueous polymerdispersion. For example, the calculated total water content may be from0.5 wt % to 1.6 wt %, 0.5 wt % to 1.5 wt %, and/or 1.0 wt % to 1.5 wt %.

The resultant viscoelastic polyurethane foam may exhibit improvedwicking effect and/or improved moisture/heat management. With respect tomoisture and heat management of a resultant foam, e.g., with respect toa viscoelastic polyurethane foam mattress or pillow, a good wickingeffect may enable sweat to move quickly away from a user's skin. The keyaspects of human body to maintain the comfort temperature are throughmoisture vapor by sweating. Sweating is the body's mechanism of keepingus cool. Good wicking effect may enable the user to remain dry and coolso as providing increased comfort. The good wicking effect may alsoprovide the sweat/water with more surface area to evaporate from. Saidin another way, as the sweat/water is dispersed over a greater area itmay evaporate more rapidly than when the water is pooled together over asmall surface area. Further, good moisture permeability may enablemoisture to leave a user's skin and enable natural moisture vapor tobring heat away from the user's skin.

For example, the viscoelastic polyurethane foam may exhibit a visuallyobservable wicking height (e.g., on a sample of the viscoelasticpolyurethane foam having the dimensions of 1.0 inch×0.5 inch×2.0 inch,when an edge of the sample is submersed in 5.0 mm of dyed water) that isgreater than a visually observable wicking height of a sample of adifferent viscoelastic polyurethane foam (which sample has the samedimensions) that is prepared using the same isocyanate-component, thesame calculated total water content, and the same isocyanate-reactivecomponent, except that the preformed aqueous polymer dispersion isexcluded. For example, the wicking height may be greater by a factor ofat least 3 (e.g., may be 3 to 10 times greater and/or 3.5 to 5.5 timesgreater).

The viscoelastic polyurethane foam may exhibit a visually observedwicking time (using a sample of the viscoelastic polyurethane foam),when three drops of dyed water are placed on a surface of the sample,that is less than a visually observed wicking time using a sample of adifferent viscoelastic polyurethane foam that is prepared using the sameisocyanate-component, the same calculated total water content, and thesame isocyanate-reactive component, except that the preformed aqueouspolymer dispersion is excluded. As would be understanding, the comparedsamples may have a same thickness/depth, but the length and width of thesamples are not dependent on the results. The wicking time is visuallyobserved as the time at which it takes for three drops of dyed water todisappear (i.e., be absorbed by the foam) away from the surface of thesamples. The wicking time may be decreased by at least 30 seconds so asto be significantly quicker when the preformed aqueous polymerdispersion is used. For example, the wicking time may be less than 5seconds for the polyurethane foam prepared using the preformed aqueouspolymer dispersion (e.g., greater than half a second).

The viscoelastic polyurethane foam may exhibit improved water vaporpermeability, e.g., as measured according to ASTM E96/E96M (andoptionally in view of ASTM E2321-03). For example, the water vaporpermeability may be improved by at least 5% (e.g., from 5% to 20%) forthe polyurethane foam prepared using the preformed aqueous polymerdispersion.

As would be understood by a person of ordinary skill in the art, theabove comparison of two different foams refers to foams prepared usingthe same process conditions, same equipment, and the same formulations,except for the exclusion of the preformed aqueous polymer dispersion andthe increased water content so as to account for excluding the preformedaqueous polymer dispersion in the comparative example.

All parts and percentages are by weight unless otherwise indicated. Allmolecular weight data is based on number average molecular weight,unless indicated otherwise.

Examples

The data and descriptive information provided herein are based onapproximations. Further, the materials principally used are as thefollowing:

AD 1 An aqueous acid polymer dispersion including approximately 21.7 wt% of a potassium hydroxide neutralized ethylene- acrylic acid copolymersalt and 78.3 wt % of water, made using a twin screw extruder and adilution scheme as described in U.S. Pat. No. 8,318,257, is prepared asfollows: A first feed includes 100 wt % of PRIMACOR ™ 5986 (an ethyleneacrylic acid resin having approximately 20.5 wt % of acrylic acid) at aflow rate of 234 lb/h, a second feed includes 100 wt % of potassiumhydroxide at a flow rate of 125 lb/h, and a third feed includes 100 wt %of water at a flow rate of 50 lb/h. A first dilution pump feeds water at220 lb/h and a second dilution pump at 538 lb/h to achieve the desiredsolids content. The barrel/zone temperature control conditions are thefollowing: Table 1 Zone Number Temperature ° C. Zone 1 27 Zone 2 151Zone 3 147 Zone 4 148 Zone 5 161 Zone 6 149 Zone 7 107 Zone 8 109 Zone 980 Zone 10 131 Zone 11 72 Zone 12 72 AD 2 An aqueous acid polymerdispersion of approximately 32.3 wt % of an ammonium hydroxideneutralized ethylene acrylic acid copolymer salt and 67.7 wt % of water,prepared similar to as AD 1 except, the second feed is different and thedilution scheme is varied to achieve the desired higher solids content,as would be understood by one of ordinary skill in the art. AD 3 Anaqueous dispersion of an aqueous acid- modified ethylene basedcopolymer, at a solids content from 40.5 wt % to 43.5 wt %, based on thetotal weight of the aqueous dispersion (available as HYPOD ™ 8503 fromThe Dow Chemical Company and enabled with BLUEWAVE ™ Technology). AD 4An aqueous dispersion of an aqueous acid- modified polyolefin polymer,at a solids content from 54 wt % to 58 wt %, based on the total weightof the aqueous dispersion (available as HYPOD ™ XU-36534 from The DowChemical Company and enabled with BLUEWAVE ™ Technology). Polyol 1 Apolyoxypropylene polyether polyol, having a nominal hydroxylfunctionality of 3 and a number average molecular weight ofapproximately 1000 g/mol (available as VORANOL ™ 3150 from The DowChemical Company). Polyol 2 A glycerine initiated polyoxyethylene-polyoxypropylene polyether polyol, having an ethylene oxide content ofapproximately 60 wt %, a nominal hydroxyl functionality of 3, primaryhydroxyl content of approximately 35%, and a number average molecularweight of approximately 1000 g/mol. Polyol 3 Anpolyoxypropylene-polyoxyethylene polyether polyol initiated withglycerine, having an ethylene oxide content of less than 20 wt %, anominal hydroxyl functionality of 3, and a number average molecularweight of approximately 3100 g/mol (available as VORANOL ™ 3136 from TheDow Chemical Company). Isocyanate A polymeric methylene diphenyldiisocyanate - PMDI (available as PAPI ™ 94 from The Dow ChemicalCompany). Surfactant An organosilicone surfactant (available as Niax ™L-618 from Momentive Performance Materials). Amine 1 A tertiary aminecatalyst (available Dabco ® BL-11 from Air Products). Amine 2 A tertiaryamine catalyst (available as Dabco ® 33-LV from Air Products). Tin A tincatalyst (available as KOSMOS ® 29 from Evonik Industries). DI DeionizedWater.

Working Examples 1 to 3 and Comparative Examples A and B are preparedaccording to the approximate formulations in Table 2, below. In theExamples below, the total formulation mass is set to be 1900 grams.Working Examples 1 to 3 are prepared using one of AD 1 and AD 2, whichare preformed aqueous acid dispersions. Comparative Example A isprepared using only water, i.e., not using a dispersion. ComparativeExample B is an attempt at preparing a viscoelastic foam usingethylene-acrylic acid copolymer and water that are added separately,i.e., not using a preformed dispersion. However, due to the inability ofethylene-acrylic acid copolymer to dissolve in water at ambientconditions (it is believed, without intending to be bound by thistheory, that a temperature of at least approximately 120° C. would beneeded to melt the ethylene-acrylic acid copolymer crystals in water)such a mixture would be non-preferred and/or unsuitable for use in afoaming reaction for forming a viscoelastic foam. In other words, it isbelieved, the high temperature required to obtain solubility would benon-preferred and/or unsuitable for the purpose herein and/ornon-dissolved ethylene-acrylic acid copolymer crystals would benon-preferred and/or unsuitable for the purpose herein. The density ofthe samples range from approximately 2.7 to 3.0 lb/ft³ (according toASTM D 3574).

TABLE 2 Ex. 1 Ex. 2 Ex. 3 Ex. A Ex. B Isocyanate-Reactive Component(amount based on parts by weight) AD 1 1.40 1.40 — — — AD 2 — — 1.62 — —PRIMACOR ™ — — — — 1.40 5986 DI 1.10 1.10 1.10 2.20 2.20 Polyol 1 20.0020.00 20.00 20.00 20.00 Polyol 2 60.00 60.00 60.00 60.00 60.00 Polyol 320.00 20.00 20.00 20.00 20.00 Surfactant 0.80 0.80 0.80 0.80 0.80 Amine1 0.15 0.15 0.15 0.15 0.15 Amine 2 0.05 0.05 0.05 0.05 0.05 Tin 0.050.05 0.05 0.05 0.05 Isocyanate Component (amount based on parts byweight) Isocyanate 53.35 52.01 53.35 53.35 53.35 Composition PropertiesApproximate 156 156 157 156 156 Total Parts Index 80 78 80 80 80 AD wt %in 1.35 1.35 1.56 — — Isocyanate- Reactive Component Calculated 2.202.20 2.20 2.20 2.20 Total Water Content (parts by weight) FoamProperties Air Flow (scfm) 8.5 8.4 7.9 3.4 * Average 5.2 — 4 4 *Resiliency (%) Recovery Time 3 5 3 3 * (seconds) IFD @ 25% 8.2 9.9 7.814.0 * Deflection (lb) IFD @ 65% 17.6 21.1 16.1 28.3 * Deflection (lb)IFD @ 25% 7.1 8.3 6.9 12.5 * Return (lb) * Unable to form a viscoelasticfoam because the PRIMACOR ™ 5986 did not dissolve in water at ambientconditions.

Working Examples 4 to 11 and Comparative Example C are preparedaccording to the approximate formulations in Table 3, below. In theExamples below, the total formulation mass is set to be 1900 grams.Working Examples 4 to 11 are prepared using one of AD 3 and AD 4, whichare preformed aqueous acid-modified polyolefin dispersion. ComparativeExample C is prepared using only water, i.e., not using a dispersion.The density of the samples range from approximately 2.5 to 3.0 lb/ft³(according to ASTM D 3574).

TABLE 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 Ex. 9 Ex. 10 Ex. 11 Ex. 12 Ex. CIsocyanate-Reactive Component (amount based on parts by weight) AD 32.20 0.77 0.77 1.91 — — — — 1.91 — AD 4 — — — — 0.51 1.01 1.52 2.53 — —DI 1.10 1.98 1.76 1.10 1.98 1.76 1.54 1.10 1.10 2.20 Polyol 1 15.0015.00 15.00 15.00 15.00 15.00 15.00 15.00 20.00 15.00 Polyol 2 60.0060.00 60.00 60.00 60.00 60.00 60.00 60.00 60.00 60.00 Polyol 3 25.0025.00 25.00 25.00 25.00 25.00 25.00 25.00 20.00 25.00 Surfactant 0.800.80 0.80 0.80 0.80 0.80 0.80 0.80 0.80 0.80 Amine 1 0.15 0.15 0.15 0.150.15 0.15 0.15 0.15 0.15 0.15 Amine 2 0.05 0.05 0.05 0.05 0.05 0.05 0.050.05 0.05 0.05 Tin 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05Isocyanate Component (amount based on parts by weight) Isocyanate 51.0050.99 50.99 50.99 50.99 50.99 50.99 50.99 51.48 50.99 CompositionProperties Approximate 155 154 155 155 155 155 155 155 156 154 TotalParts Index 75 78 78 78 78 78 78 78 77 78 AD wt % in 2.11 0.74 0.74 1.840.50 0.97 1.46 2.42 1.84 — Isocyanate- Reactive Component Calculated2.37 2.20 2.20 2.20 2.20 2.20 2.20 2.20 2.20 2.20 Total Water Content(parts by weight total) Foam Properties Air Flow 8.9 5.6 6.2 9.7 5.4 6.17.3 9.6 7.3 4.1 (scfm) Average 6 4 4 5 3 4 4 4 5 3 Resiliency (%)Recovery Time 7 3 3 5 3 4 4 4 2 3 (seconds) IFD @ 25% 5.2 8.4 8.3 5.98.8 8.8 7.9 5.8 11.4 10.7 Deflection (lb) IFD @ 65% 11.6 18.6 18.4 13.219.1 19.2 17.3 13.2 25.9 22.6 Deflection (lb) IFD @ 25% 4.2 7.3 7.2 4.97.8 7.5 6.7 5.0 10.2 9.4 Return (lb)

For each of Working Examples 1 to 11 and Comparative Examples A to C,foam samples are prepared by box foaming at ambient conditions, under afume hood using a 38 cm×38 cm×24 cm (15″×15″×9.5″) wooden box lined withclear plastic film. A 16-pin (4 pins each in four radial directions thatare separated by 90°) mixer at high rotation speed is used at highrotation speed setting, together with a 1 gallon cup (16.5 cm diameter,18 cm tall). The components in the Isocyanate-Reactive Component, withthe exception of the Tin catalyst, are mixed first for 15 seconds at2400 rpm. Then, the Tin catalyst is added and immediately mixed foranother 15 seconds at 2400 rpm. Next, the Isocyanate Component is addedand immediately mixed for another 3 seconds at 3000 rpm. Then, the mixedIsocyanate-Reactive Component and Isocyanate Component is poured intothe box lined with plastic film. The foam is observed as having reachedmaximum height when bubbles appear at the top surface of the foam. Oncefoaming is complete, the foam is further allowed to cure overnight underthe fume hood. Foam sample walls are discarded, and the remainingsamples are characterized.

For Working Example 12, the foam is made using a Cannon Varimax foamingmachine. The Polyol 1 and Polyol 3 are used as a blend with a ratio of1:1. The total polyol flow rate targets 110 lb/min. A foam bun is madewith the size of approximately 96 inch×52 inch×20 inch. The resultantfoam sample is cut a day after the foam is fabricated. Then, the samplesare conditioned for 24 hours before the physical property tests areperformed.

Calculated Total Water Content (parts by weight) is calculated as thetotal amount of DI (deionized water) added to the formulation plus theamount of water added to the formulation as part of the aqueousdispersion.

Air flow is a measure of the air that is able to pass through the foamunder a given applied air pressure. Air flow is measured as the volumeof air which passes through a 1.0 inch (2.54 cm) thick×2 inch×2 inch(5.08 cm) square section of foam at 125 Pa (0.018 psi) of pressure.Units are expressed in standard cubic feet per minute (scfm). Arepresentative commercial unit for measuring air flow is manufactured byTexTest AG of Zurich, Switzerland and identified as TexTest Fx3300.Herein, air flow is measured according to ASTM D 3574.

Average resiliency is measured according to ASTM D 3574, in particularusing the ball rebound test. Recovery time is measured is measured byreleasing/returning the compression load head from a 75% position (i.e.,the foam sample is compressed to 100% minus 75% of the sample's originalthickness) to the position where foam compression is to a 10% position(based on the original thickness of the foam sample). The Recovery Timeis defined as the time from the releasing/returning the compression loadhead to the moment that the foam pushes back against the load head witha force of at least 1 newton.

IFD is referred to as indentation force deflection and it is measuredaccording to ASTM D 3574. IFD is defined as the amount of force inpounds required to indent a fifty square inch circular plate sample acertain percentage of the sample's original thickness. Herein, IFD isspecified as the number of pounds at 25% deflection and at 65%deflection for the foam sample. Lower IFD values are sought forviscoelastic foams. For example, an IFD at 25% from 6 to 12 may be usedfor bed pillows, thick back pillows, etc. An IFD at 25% from 12 to 18may be used for medium thickness back pillows, upholstery padding, etc.An IFD at 25% from 18 to 24 may be used for thin back pillows, tuftingmatrix, very thick seat cushions, etc. An IFD at 25% greater than 24 maybe used for average to firmer seat cushions, firm mattresses, shockabsorbing foams, packaging foams, carpet pads, and other uses requiringultra-firm foams.

IFD at 25% Return is the ability of the foam to recover. In particular,the IFD at 25% Return is measured as the percentage of the IFD at 25%that is recovered after cycling through the IFD at 65% measurement andreturning to 25% compression.

As used herein, the term “tear strength” is used herein to refer to themaximum average force required to tear a foam sample which ispre-notched with a slit cut lengthwise into the foam sample. The testresults are determined according to the procedures of ASTM D3574-F inpound-force per linear inch (lbf/in) or in Newtons per meter (N/m).

Wicking Effect and Moisture/Heat Management

Working Example 12 is further evaluated for wicking and moisture/heatmanagement, as combined with the high airflow. To test the wickingwetting effect, Comparative Example D is prepared using the same methodand formulation as Working Example 12, except Additive 3 is not added tothe formulation.

To realize a good wicking effect, the materials should have a goodwetting effect. FIG. 2 illustrates the wetting effect on the foam sampleof Working Example 12 and FIG. 3 illustrates the wetting effect on thefoam sample of Comparative Example D. To perform the wetting effect,three drops of dyed water are put on the surface of the respective foamsamples having a thickness of 1.0 inch and the time at which it takesfor the drops of water to disappear from the surface is visuallyobserved and recorded as the wicking time. The water is dyed with anorange dye available from Milliken Chemical. Working Example 12 isvisually observed to have a faster wicking speed and the water drops arewicked away from the surface of the sample at a wicking time ofapproximately 1 second and Comparative Example D is visually observed tohave a slower wicking speed with a wicking time of 38 seconds.Accordingly, it is seen that when the foam samples for are made usingthe same conditions and formulations, except that the preformed aqueouspolymer dispersion is excluded in the comparative example, that thewicking speed is quicker and the wicking time is lower by approximately37 seconds, when the preformed aqueous polymer dispersion is included.

Wicking height may also be testing using a vertical wicking test. Inparticular, foam samples having the dimensions of 1.0 inch×0.5 inch×2.0inch are prepared for Working Example 12 and Comparative Example D. Thetips of the foam samples are immersed in 5.0 mm of the dyed water, whilethe foam samples are maintain in a substantially vertical positionrelative to the horizontal dish holding the dyed water. Verticalwicking, i.e., upward movement, of the water is enabled for 1 minute (atambient conditions). Then, the upward movement is measured using a rulerand recorded as the vertical wicking height. Working Example 12 ismeasured as having a vertical wicking height of 6.35 mm and ComparativeExample D is measured as having a vertical wicking height of 1.59 mm.Accordingly, it is seen that when the foam samples are made using thesame conditions and formulations, except that the preformed aqueouspolymer dispersion is excluded in the comparative example, that thewicking height is increased by a factor of approximately 4 when thepreformed aqueous polymer dispersion is included.

The water vapor permeability of Working Example 12 and ComparativeExample D may be testing. In particular, a standard cup desiccant methodis conducted following ASTM E96/E96M. Further, ASTM E2321-03 is followedfor the Standard Practice, a petri dish method (the diameter of thepetri dish is 5.5 inch). For testing each of Working Example 12 andComparative Example D, three specimens are used, of which specimens arefoam samples that have a thickness of approximately 1.30 inches and thathave their edges sealed with wax (e.g., wax that is melted atapproximately 140° F.). To test the water vapor permeability, the petridish is filled up to within ¼ in of the top rim. During testing thehumidity level is 72.7% and the temperature control is 50.8° F.

Working Example 12 is observed as having a water vapor permeability ofapproximately 71.6 (grains/hour/ft²)/ΔP×inches and Comparative Example Dis observed as having a significantly lower water vapor permeability ofapproximately 67.4 (grains/hour/ft²)/ΔP×inches. Accordingly, it is seenthat when the foam samples are made using the same conditions andformulations, except that the preformed aqueous polymer dispersion isexcluded in the comparative example, that the water vapor permeabilitymay be improved by approximately 5.9% when the preformed aqueous polymerdispersion is included.

The invention claimed is:
 1. A reaction system for forming aviscoelastic polyurethane foam that has a resiliency of less than orequal to 20% as measured according to ASTM D 3574, the reaction systemcomprising: an isocyanate component that includes at least oneisocyanate, an isocyanate index of the reaction system being from 50 to110; and an isocyanate-reactive component that is a mixture formed byadding at least a polyol component, an additive component, and apreformed aqueous polymer dispersion, the mixture including: from 50.0wt % to 99.8 wt % of a polyol component, based on the total weight ofthe mixture, the polyol component including at least one polyetherpolyol, from 0.1 wt % to 50.0 wt % of an additive component, based onthe total weight of the mixture, that includes at least one catalyst,and from 0.1 wt % to 6.0 wt % of a preformed aqueous polymer dispersion,based on the total weight of the mixture, the preformed aqueous polymerdispersion having a solids content from 10 wt % to 80 wt %, based on thetotal weight of the preformed aqueous polymer dispersion, and being oneof an aqueous acid polymer dispersion or an aqueous acid-modifiedpolyolefin polymer dispersion in which the polyolefin is derived from atleast one C₂ to C₂₀ alpha-olefin.
 2. The reaction system as claimed inclaim 1, wherein the preformed aqueous polymer dispersion is acontinuous liquid phase component at ambient conditions of roomtemperature and atmospheric pressure and is derived from a liquid phaseand a solid phase, the liquid phase being water and the solid phasebeing an acid-modified polyolefin in which the polyolefin is derivedfrom at least one C₂ to C₂₀ alpha-olefin.
 3. The reaction system asclaimed in claim 1, wherein the preformed aqueous polymer dispersion isa continuous liquid phase component at ambient conditions of roomtemperature and atmospheric pressure and is derived from a liquid phaseand a solid phase, the liquid phase being water and the solid phaseincluding an ethylene-acrylic acid copolymer.
 4. The reaction system asclaimed in claim 1, wherein the preformed aqueous polymer dispersion isseparately provided from the polyol component and the additivecomponent.
 5. The reaction system as claimed in claim 1, wherein theadditive component includes at least one surfactant.
 6. The reactionsystem as claimed in claim 1, wherein the additive component includeswater that accounts for less than 2.0 wt % of the total weight ofmixture.
 7. The reaction system as claimed in claim 1, wherein thepolyol component includes at least one polyoxyethylene-polyoxypropylenepolyether polyol that has an ethylene oxide content of at least 50 wt %,has a nominal hydroxyl functionality from 2 to 4, and accounts for 35 wt% to 90 wt % of the isocyanate-reactive component.
 8. The reactionsystem as claimed in claim 1, wherein the polyol component includes ablend of at least three polyols, the blend including: (i) apolyoxyethylene-polyoxypropylene polyether polyol that has an ethyleneoxide content of at least 50 wt %, has a nominal hydroxyl functionalityfrom 2 to 4, has a number average molecular weight from 700 g/mol to1500 g/mol, and accounts for 35 wt % to 90 wt % of theisocyanate-reactive component, (ii) a polyoxypropylene-polyoxyethylenepolyether polyol that has an ethylene oxide content of less than 20 wt%, has a nominal hydroxyl functionality from 2 to 4, has a numberaverage molecular weight greater than 1500 g/mol and less than 6000g/mol, and accounts for 5 wt % to 50 wt % of the isocyanate-reactivecomponent, and (iii) a polyoxypropylene polyether polyol that has anominal hydroxyl functionality from 2 to 4, has a number averagemolecular weight from 700 g/mol to 1500 g/mol, and accounts for 5 wt %to 50 wt % of the isocyanate-reactive component.
 9. A viscoelasticpolyurethane foam that has a resiliency of less than or equal to 20%, asmeasured according to ASTM D 3574, prepared using the reaction system asclaimed in claim 1, the viscoelastic foam having an air flow of at least5.0 ft³/min as measured according to ASTM D3574, and a recovery time ofless than 20 seconds.
 10. The viscoelastic polyurethane foam as claimedin claim 9, wherein a visually observed wicking height of a sample ofthe viscoelastic polyurethane foam, having the dimensions of 1.0inch×0.5 inch×2.0 inch, when an edge of the sample is submersed in 5.0mm of dyed water, is greater than a visually observed wicking height ofa similar sample of a viscoelastic polyurethane foam, which similarsample as the same dimensions, that is prepared using the sameisocyanate-component, a same calculated total water content, and thesame isocyanate-reactive component, except that the preformed aqueouspolymer dispersion is excluded.
 11. The viscoelastic polyurethane foamas claimed in claim 9, wherein using a sample of the viscoelasticpolyurethane foam, a visually observed wicking time, when three drops ofdyed water are placed on a surface of the sample, is less than avisually observed wicking time using a similar sample of a viscoelasticpolyurethane foam, which similar sample as the same dimensions, that isprepared using the same isocyanate-component, a same calculated totalwater content, and the same isocyanate-reactive component, except thatthe preformed aqueous polymer dispersion is excluded.
 12. A method forforming a viscoelastic polyurethane foam that has a resiliency of lessthan 20% as measured according to ASTM D 3574, the method comprising:preparing an isocyanate-reactive component by mixing at least a polyolcomponent, an additive component, and a preformed aqueous dispersion,the resultant mixture including: from 50.0 wt % to 99.8 wt % of a polyolcomponent, based on the total weight of the mixture, the polyolcomponent including at least one polyether polyol, from 0.1 wt % to 50.0wt % of an additive component, based on the total weight of the mixture,that includes at least one catalyst and at least one surfactant, andfrom 0.1 wt % to 6.0 wt % of a preformed aqueous polymer dispersion,based on the total weight of the mixture, the preformed aqueous polymerdispersion having a solids content from 10 wt % to 80 wt % based on thetotal weight of the preformed aqueous polymer dispersion and being oneof an aqueous acid polymer dispersion or an aqueous acid-modifiedpolyolefin polymer dispersion in which the polyolefin is derived from atleast one C₂ to C₂₀ alpha-olefin; providing an isocyanate component thatincludes at least one isocyanate such that an isocyanate index of thereaction system is from 50 to 110; and allowing the isocyanate componentto react with the isocyanate-reactive component to form the viscoelasticpolyurethane foam.